Plasmodium falciparum resistance to artemisinin and its derivatives is spreading in South-East Asia, and there is growing concern that this may reach other endemic countries. Methods used to assess P. falciparum resistance to artemisinin-based combination therapies (ACTs) are multiple and often divergent. This paper is a review of online accessible research publications from the past 20 years on ACTs, ranging from in vivo, in vitro/ex-vivo, molecular markers and pharmacokinetics studies. We highlight the procedures of the four main methods used for ACTs efficacy testing and provide a summary of published data. This review indicates that the most used method for ACT efficacy testing is the in vivo 28 days follow-up with molecular correction; the most widely used and reliable in vitro and ex-vivo method for artemisinin phenotyping is the ring stage survival assay from 0 to 3 h ring (RSA0-3h), and the main molecular marker of P. falciparum resistance to artemisinins are mutations on P. falciparum Kelch 13 propeller domain. Day 7 pharmacokinetics could help to predict resistance to artemether-lumefantrine and dihydroartemisinin-piperaquine. Findings from this review support that the combination of in vivo, in vitro/ex-vivo, molecular markers of drug resistance and day 7 PK levels of the partner drugs may be required for the optimal surveillance of artemisinin-based combination therapy efficacy in the field.